KR20130038266A - Transmission power dependent imbalance compensation for multi-antenna systems - Google Patents

Abstract

Methods and apparatuses for wireless communication are provided. In one aspect, transmissions from multiple antennas of the user equipment are received and a differential power control message is sent based on an imbalance of power transmitted from the multiple antennas. In another aspect, a differential power control message is received that is based on an imbalance of power transmitted from multiple antennas of a user equipment and based on this message, by varying the transmit power from one or more of the multiple antennas. Imbalance is compensated.

Description

TRANSMISSION POWER DEPENDENT IMBALANCE COMPENSATION FOR MULTI-ANTENNA SYSTEMS}

This patent application claims the benefit of US Patent Provisional Serial No. 61 / 332,654, filed May 7, 2010, entitled "Transmission Power Dependent Imbalance Compensation For Multi-Antenna Systems," which is directed to the assignee of the present application. And are hereby expressly incorporated herein by reference.

Certain aspects of the present disclosure relate generally to wireless communications, more specifically combining the benefits of preservation of battery life at high power levels with improved link efficiency at low power levels obtained by imbalance compensation. It's about doing.

Wireless communication systems are widely deployed to provide various types of communication content such as voice and data. These systems may be multiple access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems are code division multiple access (CDMA) systems, time divisional multiple access (TDMA) systems, frequency division multiple access (FDMA) systems 3GPP Long Term Evolution (LTE) systems and Orthogonal Frequency Division Multiple Access (OFDMA) systems.

In general, a wireless multiple-access communication system can simultaneously support communication for multiple terminals. Each terminal communicates with one or more base stations via transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the terminals, and the reverse link (or uplink) refers to the communication link from the terminals to the base stations. Such communication links may be established through a single-input-single-output, multiple-input-single-output or multiple-input-multi-output (MIMO) system.

Wireless standards may include power control techniques that control and limit the transmit power used by each user equipment (UE) for uplink transmission. For example, the power control technique defined in the LTE standard generates one, common power value for each UE that can be used for both antennas of the UE. However, different antennas of the UE may experience different fading environments at different points in time.

Certain aspects of the present disclosure provide a method for wireless communications. The method includes receiving transmissions from multiple antennas of the user equipment and transmitting a differential power control message based on an imbalance of power transmitted from the multiple antennas.

Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus includes means for receiving transmissions from multiple antennas of the user equipment and means for transmitting a differential power control message based on an imbalance of power transmitted from the multiple antennas.

Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus includes at least one processor configured to receive transmissions from multiple antennas of the user equipment and to transmit a differential power control message based on an imbalance of power transmitted from the multiple antennas.

Certain aspects provide computer-program objects for wireless communications. This computer-program product allows a computer to receive transmissions from multiple antennas of the user equipment and to transmit a differential power control message based on a perceived unbalance of power transmitted from the multiple antennas. A computer-readable storage medium on which instructions for storing are stored.

Certain aspects of the present disclosure provide a method for wireless communications. The method receives from the base station a transmit power from one or more of the plurality of antennas based on the message and the step of receiving a differential power control message based on an imbalance of power transmitted from the plurality of antennas of the user equipment. Compensating for the imbalance by changing.

Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus is adapted to vary the transmit power from one or more of the plurality of antennas based on the message and means for receiving a differential power control message based on an imbalance of power transmitted from the plurality of antennas of the user equipment. Means for compensating for the imbalance.

Certain aspects of the present disclosure provide an apparatus for wireless communications. The apparatus generally receives a differential power control message based on an imbalance of power transmitted from multiple antennas of the user equipment, and based on the message, changes the transmit power from one or more of the multiple antennas. At least one processor configured to compensate for the imbalance.

Certain aspects provide computer-program objects for wireless communications. The computer-program product allows a computer to receive a differential power control message based on an imbalance of power transmitted from multiple antennas of the user equipment and based on the message from one or more of the multiple antennas. And a computer-readable storage medium having stored thereon instructions for compensating for imbalance by varying the transmit power.

Various aspects and features of the disclosure are described in further detail below.

DETAILED DESCRIPTION A more detailed description briefly summarized above may be made with reference to aspects in a manner that the enumerated features of the present disclosure may be understood in detail, some of which are illustrated in the accompanying drawings. It should be noted, however, that the appended drawings illustrate only certain exemplary aspects of the present disclosure and should not be regarded as limiting the scope of the present disclosure, since the present disclosure may recognize other equally valid aspects.
1 illustrates a block diagram of a multiple access wireless communication system, in accordance with certain aspects of the present disclosure.
2 illustrates a block diagram of a wireless communication system, in accordance with certain aspects of the present disclosure.
3 illustrates a relationship of multi-state power amplifier (PA) current to P _out , in accordance with certain aspects of the present disclosure.
4 illustrates a user equipment (UE) and a base station, in accordance with certain aspects of the present disclosure.
5 illustrates a method for transmitting a differential power control message (DPCM) based on a perceived imbalance of power transmitted from multiple antennas of a UE, in accordance with certain aspects of the present disclosure.
6 illustrates a method for compensating for an imbalance in power transmitted from multiple antennas of a UE upon receipt of a DPCM, in accordance with certain aspects of the present disclosure.
7 illustrates test points for conducted and radiated power, in accordance with certain aspects of the present disclosure.
8 illustrates different antenna imbalance sources, in accordance with certain aspects of the present disclosure.
9 illustrates path loss terms for different base stations, in accordance with certain aspects of the present disclosure.
10 illustrates power control reference points, in accordance with certain aspects of the present disclosure.

In multi-antenna transmission systems, the power received from multiple antennas may not be the same. Examples contributing to power imbalance include UE power setting errors, antenna gain imbalance (AGI), shadowing, body losses and short and long term fade. In some aspects, this imbalance can be compensated for by applying a correction fed back from the receiver. Making such a modification may be satisfactory at low transmit power levels but may be detrimental to power consumption and battery life at high transmit power levels. In some aspects, this modification may be a function of the current transmit power as well as a function of the imbalance observed and fed back by the receiver. The current transmit power can be known exactly by the transmitter, so that range compression of the imbalance compensation at high power levels can be performed by the transmitter.

The techniques described herein include code division multiple access (CDMA) networks, time division multiple access (TDMA) networks, frequency division multiple access (FDMA) networks, orthogonal FDMA (OFDMA) networks, single carrier FDMA (SC) -FDMA: can be used in various wireless communication networks, such as Single-Carrier FDMA) networks. The terms "networks" and "systems" are often used interchangeably. CDMA networks may implement wireless technologies such as Universal Terrestrial Radio Access (UTRA), CDMA2000, and the like.

등과 같은 무선 기술을 구현할 수 있다. UTRA, E-UTRA 및 GSM은 범용 모바일 통신 시스템(UMTS: Universal Mobile Telecommunication System)의 일부이다. LTE는 E-UTRA를 사용하는 UMTS의 릴리스(release)이다. UTRA, E-UTRA, GSM, UMTS 및 LTE는 "3세대 파트너십 프로젝트"(3GPP: 3rd Generation Partnership Project)로 명명된 조직으로부터의 문서들에 기술되어 있다. CDMA2000은 "3세대 파트너십 프로젝트 2"(3GPP2)로 명명된 조직으로부터의 문서들에 기술되어 있다. 명확성을 위해, 이러한 기술들의 특정 양상들은 아래에서 LTE에 관해 설명되며, 아래 설명의 대부분에서 LTE 전문 용어가 사용된다.UTRA includes wideband CDMA (W-CDMA) and Low Chip Rate (LCR). CDMA2000 covers IS-2000, IS-95 and IS-856 standards. TDMA networks can implement wireless technologies such as Global System for Mobile Communications (GSM). OFDMA networks include Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDM

Wireless technology such as UTRA, E-UTRA and GSM are part of the Universal Mobile Telecommunication System (UMTS). LTE is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS and LTE are described in documents from an organization named "3rd Generation Partnership Project" (3GPP). CDMA2000 is described in documents from an organization named "3rd Generation Partnership Project 2" (3GPP2). For clarity, certain aspects of these techniques are described below with respect to LTE, and LTE terminology is used in much of the description below.

Single carrier frequency division multiple access (SC-FDMA) uses single carrier modulation and frequency domain equalization. The SC-FDMA signal has a lower peak-to-average power ratio (PAPR) due to its inherent single carrier structure. SC-FDMA has attracted particular interest in uplink communications where lower PAPR in terms of transmit power efficiency is advantageous for mobile terminals. SC-FDMA is used for uplink multiple access in LTE.

The MIMO system uses multiple (N _T ) transmit antennas and multiple (N _R ) receive antennas for data transmission. A MIMO channel formed by the N _T transmit and N _R receive antennas may be decomposed into N _S independent channels, independent channels N _S may also be referred to wandering spatial channels, where, N _S ≤ min {N _T , N _R }. Each of the N _S independent channels corresponds to a dimension. If additional dimensionalities generated by multiple transmit and receive antennas are used, the MIMO system can provide improved performance (eg, higher throughput and / or greater reliability).

MIMO systems support Time Division Duplex (TDD) and Frequency Division Duplex (FDD) systems. In a TDD system, since the forward and reverse link transmissions are in the same frequency domain, the principle of reciprocity enables the estimation of the forward link channel from the reverse link channel. This allows the access point to extract the transmit beamforming gain on the forward link when multiple antennas are available at the access point.

Referring to FIG. 1, a multiple access wireless communication system in accordance with certain aspects of the present disclosure is illustrated. The access point 100 (AP) includes a plurality of antenna groups, one antenna group including antennas 104 and 106, another antenna group including antennas 108 and 110, and further The antenna group includes antennas 112 and 114. Although only two antennas are shown for each antenna group in FIG. 1, more or fewer antennas may be used for each antenna group. The access terminal 116 (AT) (eg, UE) communicates with the antennas 112, 114, where the antennas 112, 114 communicate information to the access terminal 116 via the forward link 120. And receive information from access terminal 116 via reverse link 118. The access terminal 122 communicates with the antennas 106 and 108, where the antennas 106 and 108 transmit information to the access terminal 122 over the forward link 126 and over the reverse link 124. Receive information from access terminal 122. In an FDD system, communication links 118, 120, 124, and 126 may use different frequencies for communication. For example, forward link 120 may use a different frequency than the frequency used by reverse link 118. In some aspects, the access terminals 116, 122 may perform the operations described above, and range compression of the imbalance compensation may be performed by the terminals 116, 122 at high power levels.

Each group of antennas and / or an area designed to communicate with them is often referred to as a sector of the access point. In one aspect, each of the antenna groups is designed to communicate with access terminals in a sector of the area covered by the access point 100.

In communication over forward links 120, 126, the transmit antennas of access point 100 determine the signal-to-noise ratio (SNR) of the forward links for different access terminals 116, 122. Use beamforming to improve. In addition, an access point that uses beamforming to transmit to access terminals randomly scattered throughout its coverage may be used to access terminals of neighboring cells compared to an access point transmitting to all its access terminals through a single antenna. Cause less interference.

An access point may be a fixed station used to communicate with terminals, and may also be referred to as a base station, Node B, evolved Node B (eNB), or some other terminology. An access terminal may also be referred to as a mobile station, UE, wireless communication device, terminal, access terminal, or some other terminology.

2 is a block diagram of an aspect of a transmitter system 210 (also referred to as an access point) and a receiver system 250 (also referred to as an access terminal) of the MIMO system 200. In the transmitter system 210, traffic data for a number of data streams is provided from a data source 212 to a transmit (TX) data processor 214.

In one aspect, each data stream is transmitted via each transmit antenna. TX data processor 214 formats, codes, and interleaves the traffic data for each data stream based on a particular coding scheme selected for each data stream to provide coded data.

The coded data for each data stream may be multiplexed with the pilot data using OFDM techniques. The pilot data is generally a known data pattern that is processed in a known manner and can be used in the receiver system to estimate the channel response. The multiplexed pilot and coded data for each data stream are then selected for a particular modulation scheme selected for each data stream (e.g., binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-). Modulation (ie, symbol mapping) is based on PSK or quadrature amplitude modulation (M-QAM) to provide modulation symbols. The data rate, coding, and modulation for each data stream may be determined by instructions performed by the processor 230. [ The memory 232 may store data and program codes for the transmitter system 210.

Next, modulation symbols for all data streams are provided to the TX MIMO processor 220, which may further process the modulation symbols (eg, for OFDM). TX MIMO processor 220 then provides N _T modulation symbol streams to N _T transmitters (TMTR) 222a through 222t. In certain aspects, TX MIMO processor 220 applies beamforming weights to the symbols and antennas of the data streams, where the antenna is the antenna transmitting this symbol.

Each transmitter 222 receives and processes each symbol stream to provide one or more analog signals, and further conditioning (eg, amplify, filter, and upconvert) the analog signals to transmit on the MIMO channel. Provide a suitable modulated signal. Next, N _T modulated signals from transmitters 222a through 222t are transmitted from N _T antennas 224a through 224t, respectively. In some aspects, the differential power control message (DPCM) 202 may be transmitted from the antennas 224a through 224t, as described further herein.

In receiver system 250, the transmitted modulated signals are received by N _R antennas 252a through 252r and the signal received from each antenna 252 is sent to each receiver (RCVR) 254a through 254r. Is provided. Each receiver 254 conditions (e.g., filters, amplifies, and downconverts) each received signal, digitizes the conditioned signal to provide samples, further processes the samples, and correspondingly "receives." Provided symbol stream.

Since, RX data processor 260 then receives and processes the N _R received symbols streams from N _R receivers 254 based on a particular receiver processing technique to provide N _T of "detected" symbol streams. The RX data processor 260 then demodulates, deinterleaves, and decodes each detected symbol stream to recover the traffic data for the data stream. Processing by the RX data processor 260 may be complementary to the processing performed by the TX MIMO processor 220 and the TX data processor 214 of the transmitter system 210.

Processor 270 periodically determines which pre-coding matrix to use. Processor 270 formulates a reverse link message comprising a matrix index portion and a rank value portion. Memory 272 may store data and program codes for receiver system 250.

The reverse link message may comprise various types of information regarding the received data stream and / or the communication link. The reverse link message is then processed by TX data processor 238 and also modulated by modulator 280, which also receives traffic data for multiple data streams from data source 236, and transmitters 254a through 254r. And is sent back to the transmitter system 210.

In transmitter system 210, modulated signals from receiver system 250 are received by antennas 224, conditioned by receivers 222, demodulated by demodulator 240, and an RX data processor. Processed by 242 to extract the reverse link message sent by receiver system 250. The processor 230 beamforms the extracted message using the pre-coding matrix. In some aspects, sounding reference signals (SRS) 204 may be transmitted by antennas 252a through 252r and measured at transmitter system 210, as described further herein. .

In multi-antenna transmission systems, the power received from multiple antennas may not be the same. Examples contributing to power imbalance include user equipment (UE) power setting errors, antenna gain imbalance (AGI), shadowing, body losses and short and long term fade. In some aspects, this imbalance can be compensated for by applying a correction fed back from the receiver. Making such a modification may be satisfactory at low transmit power levels but may be detrimental to power consumption and battery life at high transmit power levels. In some aspects, this modification may be a function of the current transmit power as well as a function of the imbalance observed and fed back by the receiver. The current transmit power can only be known exactly by the transmitter, so that range compression of the imbalance compensation at high power levels can be performed by the transmitter.

Uplink MIMO is each of a power control formulation and power control equation, such as a point of applicability of the power control equation (eg, power control for codewords, for layers, for antennas, or for total transmission). Multiple aspects of the formulation of the term of (e.g., path loss for an antenna or average path loss across antennas; for codeword, transmission format (TF) delta term for layer, or average TF delta) Can affect. In general, as in LTE, power control in LTE Advanced (LTE-A) counteracts slow fading, shadowing changes and countercell inter-cell interference coordination (ICIC), as opposed to inverting short term fades. You can aim to act as an enabler for. In-cell users can be orthogonalized (aside from multi-user MIMO), so power fluctuations can only have inter-cell effects.

In an ideal case, the average received power at the eNB from the MIMO antennas from the UE should be the same. Rel-8 power control formulations will have more or less applicability and will not need much to complete. However, for the situations described further below, the power from the MIMO antennas may not be the same. In some aspects, power control may be based on a trade-off between efficient use of UE battery power (metric A) and efficient use of E-UTRAN resources (metric B) while maximizing link throughput.

For some aspects, according to the assumption of battery consumption proportional to the output power (P _out ) (which may not be a common case), the appropriate metric is a constant long term conducted power over the antennas. sum) (metric A) may be to evaluate the link performance of the differential power control schemes. Under this condition, suitable schemes apply to channel gain weighted P _out allocation for rank 1 transmissions (and for layers mapped to multiple antennas, eg, rank 2 transmission) and to rank transmissions greater than one. Water filling for the water.

For some aspects, assuming that battery consumption is not a factor (since in low power regimes, the power amplifier (PA) power may be negligible compared to the power consumption of other UE blocks), a suitable metric would be long term radiation across the antenna. The sum of the powers given is the same (metric B) may be to evaluate the link performance of the differential power control schemes under constraint. Under this condition, since the assumption may be equivalent to removing AGI without incurring costs (except for signaling of overhead), full inversion of AGI and inversion of shadowing may lead to appropriate results. . Power control trade-offs may be different in different P _out regimes.

3 is a graph illustrating the relationship of PA current in multiple stages, in accordance with certain aspects of the present disclosure. If the UE is operating in a low power regime, the transmit chain power consumption may not dominate the UE power usage and thus may not determine battery life. For example, for P _out less than 0 dBm (eg below 302), PA power consumption may be negligible and may be governed by quiescent current (ie, may not depend on P _out ). ). For P _{out that} is greater than or equal to 0 dBm and less than 10 dBm (eg, between 302 and 304), PA power consumption may depend on P _out but may be only a medium important factor in total power consumption. . However, for P _out greater than or equal to 10 dBm (eg, between 304 and 306), PA may be an important contributor to total power consumption and PA power may be equal to the square root of P _out (eg, P _out) . Can be strongly dependent on For some aspects, for the purposes of evaluating power control strategies, for P _out greater than or equal to 10 dBm, metric A can be used (ie, efficiently using UE battery power) and for P _out less than 10 dBm , Metric B can be used (ie, efficiently using E-UTRAN resources).

4 is an exemplary system 400 having a base station (BS) 410 (eg, eNB) and a UE 420, which may perform range compression of the imbalance compensation at the high power levels described herein. ). As shown, the UE 420 may include an SRS generation module 424. The SRS generation module 424 can generate one or more SRSs to be sent to the BS 410 via the transmitter module 422. BS 410 may receive the SRS via receiver module 416. BS 410 may construct a differential power control message (DPCM) after measuring the SRS via SRS processing module 414. The DPCM may be sent to the UE 420 via the transmitter module 412.

In this manner, power imbalance at the UE 420 may be compensated by applying the DPCM fed back from the BS 410. As described above, the compensation may be a function of the current transmission power at the UE 420 as well as a function of the imbalance observed and fed back by the BS 410. The current transmit power can only be known exactly by the UE 420, and therefore, the range compression of the imbalance compensation at high power levels can be performed by the UE 420.

5 illustrates a method 500 for transmitting a differential power control message (DPCM) based on a perceived imbalance of power transmitted from multiple antennas of a UE, in accordance with certain aspects of the present disclosure. Operations 500 may be performed by the serving eNB, for example, for transmission of DPCM.

At 502, the serving eNB may receive transmissions from multiple antennas of the UE. In some aspects, these transmissions may be SRS from each of the antennas of the UE. For other aspects, these transmissions can be a demodulation reference signal (DM-RS) from each of the antennas of the UE.

At 504, the serving eNB may transmit a DPCM based on the perceived imbalance of power transmitted from the multiple antennas.

6 illustrates a method 600 for compensating for an imbalance in power transmitted from multiple antennas of a UE upon receipt of a DPCM, in accordance with certain aspects of the present disclosure. Operations 600 may be performed by a UE, for example, for transmit power dependent imbalance compensation.

At 602, the UE may receive a differential power control message from a BS (eg, serving eNB) based on an imbalance of power transmitted from multiple antennas of the UE. In some aspects, the message may include a common value and a differential value. The common value may apply for all antennas of the UE. For some aspects, the rate of updates to the common value and the differential value may be different. For example, differential values may be received less frequently than common values.

At 604, based on the message, the UE can compensate for the imbalance by changing the transmit power from one or more of the multiple antennas. In some aspects, compensation of the imbalance can be based on a differential value. In some aspects, the compensation of the imbalance may be based on a combination of the differential value and the previously received differential values. For some aspects, compensation of the imbalance can be based on the current transmit power of the UE, as described below. In some aspects, the transmit power of the UE may remain the same upon a change in transmit power from one or more of the multiple antennas. In some aspects, the transmit power of the UE may be equal to the sum of the power transmitted from the multiple antennas of the UE. In some aspects, compensation of imbalance can be applied to the SRS from each of the plurality of antennas.

Optionally, at 606, the UE may determine path loss based on received downlink path loss measurements for each of the plurality of antennas. At 608, based on the measurement for each of the plurality of antennas, the UE may compensate for the path loss by converting transmit power from one or more of the plurality of antennas.

7 illustrates example test points for conducted and radiated power, in accordance with certain aspects of the present disclosure. Power control with and without AGI compensation can be evaluated according to, for example, 0 dB, 3 dB and 6 dB AGI. For some aspects, this assessment may be based on a comparison between throughput and signal-to-noise ratio (SNR), where the 'signal' component of the SNR is conducted using metric A and radiated power with metric B. It may be based on considering power. At high power (eg, P _out greater than or equal to 10 dBm), under metric A, AGI compensation for the antenna can reduce throughput. For example, with AGI compensation, there can be up to 2.5 dB loss at high SNR. However, at low power (eg, P _{out of} less than 10 dBm), under metric B, AGI compensation for the antenna can increase throughput. For example, with AGI compensation, there may be a maximum of 1 dB gain.

In some aspects, over the air AGI compensation capability may be added. This may be accomplished by power offset commands sent by the eNB to the UE. The offset may be interpreted as a 'static' power offset between conducted transmit power to be applied in addition to regular (ie, per codeword or total across the antennas) power control. AGI compensation can be made at a significantly lower rate than normal power control and may not require the implicit operating time of applying AGI compensation. However, due to the negative impact of AGI compensation on battery life, sliding scale or step functions can be defined for the AGI compensation range. For example, the UE

0 dB for 23 dBm> P _out ≥ 20 dBm,

2 dB for 20 dBm> P _out ≥ 15 dBm,

3 dB for 15 dBm> P _out ≥ 10 dBm, and

6 dB when 10 dBm> P _out

This can limit AGI rewards.

Transmitter AGI at the UE is a common source of long term receive power imbalance at the eNB. Although AGI may be an important factor, other sources of imbalance include UE transmitted power calibration errors, shadowing, and path loss.

8 illustrates different antenna imbalance sources, in accordance with certain aspects of the present disclosure. In the case of UE transmitted power calibration errors, at low power levels, the circuit for measuring the actual UE output power may not be effective, and thus the UE may not actually know its output power correctly. This can create imbalances, essentially without any AGI. In some aspects, these errors may be compensated for by eNB feedback. In the case of AGI, the UE may have antennas of different qualities for 'primary' and 'secondary' chains by design. The standard may set appropriate limits on this difference. In some aspects, these differences may be compensated for in a low power regime but not in a high power regime. In the case of shadowing and path loss, different UE antennas may experience different body losses, for example. However, these differences may or may not be compensated, as discussed below.

In the case of UE transmitted power calibration errors, at low power levels, the circuit for measuring the actual output power may not be effective, and thus the UE may not actually know the output power exactly. Examples of allowed UE power setting errors are given below (Table 1):

P _CMAX           ( dBm ) Tolerance T ( P _CMAX ) ( dB ) 21≤ _CMAX P ≤ 23 2.0 20 ≤ P _CMAX <21 2.5 19 ≤ P _CMAX <20 3.5 18 ≤ P _CMAX <19 4.0 13 ≤ P _CMAX <18 5.0 8 ≤ P _CMAX <13 6.0 -40 ≤ P _CMAX <8 7.0

In medium to low power regimes, the UE power setting error can be quite large, with ± 14 dB possible between the conducted powers on the two transmitter chains. The tolerance given in the table above is for UE maximum power and may not be directly applicable to UE power settings. However, they can be seen as a good indication of the expected UE absolute power setting tolerance.

Allowed (and expected) power setting errors can be quite large, but errors can be symmetric across two transmitter chains when matched components are used. If the expected relative power setting errors are large, there may be a clear use case for over-the-air relative power compensation. Unlike AGI compensation, there may be no battery life cost except for signaling overhead. However, the power setting errors may not be constant over the power range, which may make the compensation less useful when the UL RB allocation changes in size, and therefore it should also be taken into account that the power transmitted by the UE varies widely.

For some aspects, downlink (DL) path loss measurements for the antenna and open loop power control for the antenna can be enabled based on the DL measurements. The advantage of this mechanism is that both AGI and path loss differences can be compensated for automatically, without any over-the-air signaling overhead. This can make the open loop component for the antenna an attractive choice. However, as will be described below, there may be some problems with path loss compensation for the antenna.

Path loss may not capture the transmitted power calibration errors. Thus, additional closed loop compensation schemes may be required. At high power levels, path loss compensation can be detrimental to battery life, so for high power cases switching to average path loss can be beneficial.

Path loss measurements can be sensitive to receiver chain calibration errors and generally have large calibration errors. Examples of open loop power tolerance requirements are given below (Table 2):

Conditions Tolerance normal ± 9.0 dB extreme ± 12.0 dB

The tolerances are for conducted measurements. Thus, the UE may be allowed (and expected) to form large power setting errors even in the absence of AGI. Assuming the worst case, the UE can produce a fairly large ± 24 dB power imbalance of the open loop for the antenna even without AGI. Given the typical range of AGI, open loop compensation for the antenna may produce larger errors than AGI itself.

By comparing Table 1 and Table 2, approximately 2 dB to 5 dB range can be reserved for low noise amplifier (LNA) calibration errors, which may be an extraneous undesirable term for open loop path loss compensation for the antenna. . These errors can be a large degree symmetric between different transmitter chains or receiver chains.

9 illustrates path loss terms for different eNBs, in accordance with certain aspects of the present disclosure. Path loss imbalance can be different for other eNBs (interfering eNBs) that the serving eNB to the UE can interfere with, in which case the gain of link performance for the serving eNB differs for other cells (e.g., interfering eNBs). May be negated by increased interference. For example, the gain of link performance 902a, 902b to the serving eNB may be negated by increased interference 902a, 902b to the interfering eNB.

In some aspects, if the path loss differences are symmetric, i.e., the following equation,

Path Loss_00 (dB) -Path Loss_01 (dB) = Path Loss_10 (dB) -Path Loss_11 (dB)

If this is largely satisfied, path loss compensation is justified. In particular, the following conditions,

Path loss_00 (dB) -path loss_01 (dB)> 0 and

Path Loss_10 (dB) -Path Loss_11 (dB)> Path Loss_00 (dB) -Path Loss_01 (dB)

In the case of maintaining, even in absolute terms, there may be a large gain due to path loss compensation since the received signal at the serving eNB may be increased more than the interference received at the interfering eNB. However, the following conditions,

Path loss_00 (dB) -path loss_01 (dB)> 0 and

Path Loss_11 (dB) -Path Loss_10 (dB)> Path Loss_00 (dB) -Path Loss_01 (dB)

If loss is maintained, path loss compensation may be detrimental to system capabilities in some aspects because interference may increase more than the desired signal power increase. In some aspects, the application of path loss compensation for the antenna can optionally be made by L3 signaling. For some aspects, if path loss compensation for the antenna is implemented, path loss compensation may be disabled by the eNB by the UL power control configuration.

10 illustrates power control reference points 1002, 1004, 1006 for controlling power, in accordance with certain aspects of the present disclosure. Since the entire transmitter chain could be considered linear for specification purposes, the reference point for power control in Rel-8 was arbitrary. However, in Rel-10 UL MIMO, selecting different reference points may have different meanings. For example, if a particular MCS power control delta is calculated for a given codeword, the delta may be applied to the layers of the codeword or, more precisely, to the antennas associated with each of these layers. .

Rel-8 power control for the PUSCH is given as follows:

For some aspects, the following index notation is used.

i: subframe index,

k: Tx antenna index,

j: PUSCH transmission type (eg, those that are semi-persistently or dynamically scheduled, etc.), and

m: codeword index

The multi-antenna transmission scheme is as follows:

Lt; / RTI &gt;

는 안테나에 대한 최대 전력이고,

는 서브프레임 i(클러스터들에 걸쳐 합산될 수 있음)에서 유효한 물리적 업링크 공유 채널(PUSCH) 리소스 할당의 대역폭이고,

는 프리코더 스케일 팩터이고,

는 전력 오프셋이고,

는 안테나 k에 관한 경로 손실 측정치이고,

는 경로 손실 계수이고,

는 코드워드 m에 대한 서브프레임 i의 송신 포맷 델타이고,

는 전송 전력 제어(TPC)(모든 안테나들에 걸쳐 공통임)이고,

는 (안테나들 간의 상대적 전력을 단지 조정하는) 안테나에 대한 상대적 전력 제어이고,

는 다중-계층 전력 조정이고(

은 서브프레임 i 내 코드워드 m에서의 계층들의 수이다), 그리고

는 MIMO 전력 조정이다(

는 서브프레임 i 내의 계층들의 총 수이다).here,

Is the maximum power for the antenna,

Is the bandwidth of a valid physical uplink shared channel (PUSCH) resource allocation in subframe i (which may be summed across clusters),

Is the precoder scale factor,

Is the power offset,

Is the path loss measure for antenna k,

Is the path loss factor,

Is the transmission format delta of subframe i for codeword m,

Is transmit power control (TPC) (common across all antennas),

Is the relative power control for the antenna (just adjusting the relative power between the antennas),

Is a multi-layer power regulation (

Is the number of layers in codeword m in subframe i), and

Is the MIMO power adjustment (

Is the total number of layers in subframe i).

가 사용될 수 있으며, 여기서,

는 UE에서의 Tx 안테나들의 수이다. 그러나, 안테나에 대한 전력 제어가 적용되는 경우,

가 또한 다른 안테나 전송 전력들의 함수일 수 있으므로,

가 만족된다. 총 전력 제한을 유지하기 위한 안테나에 대한 스케일링은 UE 구현 의존형일 수도 있거나 또는 UE 구현 의존형이 아닐 수 있다.In some aspects,

Can be used, where

Is the number of Tx antennas at the UE. However, if power control for the antenna is applied,

Can also be a function of other antenna transmit powers,

Is satisfied. Scaling for the antenna to maintain the total power limit may or may not be UE implementation dependent.

가 서브프레임 i에서 사용된 프리코더에 의존할 수 있다.

는 턴-오프 팩터들이 효과적으로 되게 구현되도록 요구될 수 있다. 일부 양상들의 경우, 이는, 전송 프리코딩 매트릭스 표시(TPMI) 변경으로 인해 총 전력이 3dB 점프하게 한다.

May depend on the precoder used in subframe i.

May be required to be implemented so that the turn-off factors are effective. In some aspects, this causes the total power to jump 3 dB due to the transmission precoding matrix indication (TPMI) change.

는 Rx 경로들에 걸친 결합이 없는 것을 제외하고 Rel-8에서와 비슷할 수 있다. 안테나에 대한 엘리먼트들은

×1 컬럼의 벡터로 배열될 수 있다.

May be similar to that in Rel-8 except that there is no binding across the Rx paths. The elements for the antenna

Can be arranged as a vector of x1 columns.

는

계수 '매트릭스'이다. 예를 들어, 안테나에 대한 경로 손실 보상은

인 경우 인에이블된다. 다른 미리-정의된

가 가능할 수 있지만 옵션들의 수는 단지 몇 개만으로 제한될 수 있다. 경로 손실 팩터들은, 안테나들에 걸친 임의의 가중된 평균을 적용하기 전에 선형으로 컨버팅될 수 있고 이후 dB로 다시 컨버팅될 수 있다.

The

The coefficient is 'matrix'. For example, the path loss compensation for the antenna

If is enabled. Different pre-defined

May be possible, but the number of options may be limited to only a few. The path loss factors can be converted linearly before applying any weighted average across the antennas and then converted back to dB.

는 코드워드에 대해 결정될 수 있고 코드워드의 각각의 계층에 적용될 수 있다. 이후, 각각의 계층에 대한 계수가 그 계층과 연관된 각각의 안테나에 적용될 수 있다.

May be determined for the codeword and applied to each layer of the codeword. The coefficients for each layer can then be applied to each antenna associated with that layer.

는 더 느린 레이트에서 그리고 제한된 동적 범위로 전송될 수 있다.

Can be transmitted at a slower rate and in a limited dynamic range.

는

의 함수이고, 여기서

는 서브프레임 i내 코드워드 m에서의 계층들의 수이다. 이것의 목적은

의 목적과 유사하다. 그러나, (

의 경우

와 같은) 고유 계수는 상이할 수 있다. 일부 양상들의 경우,

이다.

는 서브프레임 i 내의 프리코더를 통해 계층

과 연관되는 각각의 안테나 k에 적용될 수 있다.

The

Is a function of, where

Is the number of layers in codeword m in subframe i. The purpose of this is

Is similar to the purpose. But, (

In the case of

Eigen coefficients may be different. In some aspects,

to be.

Layer through the precoder in subframe i

May be applied to each antenna k associated with

는

의 함수이고,

는 현재 서브프레임 내 SU-MIMO 계층들의 총 수이다.

는, 대략적인 제 1 송신 블록 에러 레이트(BLER)를 보장하기 위해 요구되는 전력 조정과 다수의 계층들 사이에 안정한 상관관계가 존재하는 것으로 증명되는 경우 유용할 수 있다.

The

Is a function of

Is the total number of SU-MIMO layers in the current subframe.

May be useful if it is proved that there is a stable correlation between the power adjustment and multiple layers required to ensure an approximate first transmission block error rate (BLER).

이 디스에이블될 수 있다. 다중-계층 전력 제어의 디스에이블링은, 그러나,

와 비슷한, 추가적인 시그널링된 파라미터와 함께 달성될 수 있다.In the formulation, multi-layer power control adjustment

This can be disabled. Disabling multi-layer power control, however,

Similar to, can be achieved with additional signaled parameters.

에 대한 계산 방법은 다음과 같이 Rel-8에서 지정되었는데,

The calculation method for was specified in Rel-8 as follows:

의 경우

이고

인 경우 0이며,

In the case of

ego

If is 0,

와 같이 계산된다.Where MPR is

Is calculated as

In the MIMO case, this may be changed as it applies to each codeword m (maximum 2) separately.

은 here

silver

Is calculated.

는 코드워드 m에서의 계층들의 수이다.

Is the number of layers in codeword m.

Various operations of the methods described above may be performed by various hardware and / or software component (s). The various illustrative logic blocks, modules, and circuits described in connection with the present disclosure can be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate array (FPGA) signals, or other programmable logic. It may be implemented or performed in a device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may include a microprocessor, but in the alternative, the processor may include any commercially available processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, eg, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors coupled to a DSP core, or any other such configuration. .

The steps of a method or algorithm described in connection with the present disclosure may be implemented directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may reside in any form of storage medium known in the art. Some examples of storage media that can be used include random access memory (RAM), read-only memory (ROM), flash memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM, and the like. The software module may include a single instruction or many instructions and may be distributed through several different code segments between different programs and across multiple storage media. The storage medium may be coupled to the processor such that the processor can read information from, and write information to, the storage medium. Alternatively, the storage medium may be integrated into the processor.

The methods disclosed herein comprise one or more steps or actions for achieving the described method. Method steps and / or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions may be modified without departing from the scope of the claims.

The software or commands may also be transmitted via a transmission medium. For example, if the software is transmitted from a web site, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies (such as infrared, radio, and microwave), Coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies (such as infrared, radio and microwave) are included in the definition of transmission media.

In addition, it is recognized that the modules and / or other suitable means for performing the methods and techniques described herein may be downloaded and / or otherwise obtained by the base station and / or the terminal as applicable. Should be. For example, such a device may be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, the various methods described herein may be provided via storage means (eg, a physical storage medium such as a RAM, ROM, compact disc (CD) or floppy disk, etc.), such that a user terminal and / or base station Can obtain various methods upon coupling or providing the storage means to the device. In addition, any other suitable technique for providing the methods and techniques described herein to a device can be utilized.

It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims (50)

A method for wireless communications,
Receiving transmissions from multiple antennas of the user equipment; And
Transmitting a differential power control message based on an imbalance of power transmitted from the plurality of antennas. The method of claim 1,
Wherein the message includes a common value and a differential value. The method of claim 2,
The differential value is transmitted less frequently than the common value. The method of claim 1,
Receiving the transmissions comprises receiving one of a sounding reference signal and a demodulation reference signal from each of the plurality of antennas. An apparatus for wireless communications,
Means for receiving transmissions from multiple antennas of the user equipment; And
Means for transmitting a differential power control message based on an imbalance of power transmitted from the plurality of antennas. The method of claim 5, wherein
And the message includes a common value and a differential value. The method according to claim 6,
And the differential value is transmitted less frequently than the common value. The method of claim 5, wherein
Means for receiving the transmissions comprises means for receiving one of a sounding reference signal and a demodulation reference signal from each of the plurality of antennas. An apparatus for wireless communications,
At least one processor configured to receive transmissions from the plurality of antennas of the user equipment and to transmit a differential power control message based on an imbalance of power transmitted from the plurality of antennas. The method of claim 9,
And the message includes a common value and a differential value. 11. The method of claim 10,
And the differential value is transmitted less frequently than the common value. The method of claim 9,
And the at least one processor is configured to receive one of a sounding reference signal and a demodulation reference signal from each of the plurality of antennas. A computer-program product comprising a computer-readable storage medium, comprising:
The computer-
Instructions for causing a computer to receive transmissions from multiple antennas of the user equipment; And
Computer-readable storage medium comprising instructions for causing the computer to transmit a differential power control message based on an imbalance of power transmitted from the plurality of antennas. The method of claim 13,
And the message comprises a common value and a differential value. 15. The method of claim 14,
And the differential value is transmitted less frequently than the common value. The method of claim 13,
Instructions for causing the computer to receive the transmissions include instructions for causing the computer to receive one of a sounding reference signal and a demodulation reference signal from each of the plurality of antennas. A computer-program product comprising a medium. A method for wireless communications,
Receiving a differential power control message based on an imbalance of power transmitted from multiple antennas of a user equipment (UE); And
Based on the message, compensating for the imbalance by varying transmit power from one or more of the plurality of antennas. The method of claim 17,
Wherein the message includes a common value and a differential value. The method of claim 18,
And the differential value is received less frequently than the common value. The method of claim 18,
Compensating for the imbalance is based on the differential value. The method of claim 18,
Compensating for the imbalance is based on a combination of the differential value and a previously received differential value. The method of claim 17,
Compensating for the imbalance is further based on the current transmit power of the UE. The method of claim 17,
And wherein the transmit power of the UE remains substantially the same upon a change in the transmit power from one or more of the plurality of antennas. 24. The method of claim 23,
And the transmit power of the UE is equal to the sum of the transmit powers from the plurality of antennas of the UE. The method of claim 17,
Determining path loss based on received downlink path loss measurements for each of the plurality of antennas; And
Based on the measurement for each of the plurality of antennas, compensating for the path loss by varying transmit power from one or more of the plurality of antennas. The method of claim 17,
Transmitting one of a sounding reference signal (SRS) and a demodulation reference signal (DM-RS) from each of the plurality of antennas. The method of claim 26,
The step of compensating for the imbalance is applied to one of the SRS and the DM-RS from each of the plurality of antennas. An apparatus for wireless communications,
Means for receiving a differential power control message based on an imbalance in power transmitted from multiple antennas of a user equipment (UE); And
Based on the message, means for compensating for the imbalance by varying transmit power from one or more of the plurality of antennas. 29. The method of claim 28,
And the message includes a common value and a differential value. 30. The method of claim 29,
And the differential value is received less frequently than the common value. 30. The method of claim 29,
The means for compensating for the imbalance is based on the differential value. 30. The method of claim 29,
Means for compensating for the imbalance is based on a combination of the differential value and a previously received differential value. 29. The method of claim 28,
Means for compensating for the imbalance is further based on a current transmit power of the UE. 29. The method of claim 28,
Wherein the transmit power of the UE remains substantially the same upon a change in the transmit power from one or more of the plurality of antennas. 35. The method of claim 34,
And the transmit power of the UE is equal to the sum of the transmitted power from the plurality of antennas of the UE. 29. The method of claim 28,
Means for determining path loss based on received downlink path loss measurements for each of the plurality of antennas; And
And means for compensating for the path loss by varying transmit power from one or more of the plurality of antennas based on the measurement for each of the plurality of antennas. 29. The method of claim 28,
Means for transmitting one of a sounding reference signal (SRS) and a demodulation reference signal (DM-RS) from each of the plurality of antennas. 39. The method of claim 37,
And means for compensating for the imbalance is applied to one of the SRS and the DM-RS from each of the plurality of antennas. An apparatus for wireless communications,
Receive a differential power control message based on an imbalance of power transmitted from multiple antennas of a user equipment (UE), and change the transmit power from one or more of the multiple antennas based on the message. At least one processor configured to compensate for the imbalance by doing so. 40. The method of claim 39,
And the message includes a common value and a differential value. 41. The method of claim 40,
Compensating for the imbalance is based on the differential value. 41. The method of claim 40,
Compensating for the imbalance is based on a combination of the differential value and a previously received differential value. 40. The method of claim 39,
Compensating for the imbalance is further based on the current transmit power of the UE. 40. The method of claim 39,
Wherein the at least one processor comprises:
Determine path loss based on received downlink path loss measurements for each of the plurality of antennas; And
Based on the measurement for each of the plurality of antennas, further configured to compensate for the path loss by varying transmit power from one or more of the plurality of antennas. A computer-program product comprising a computer-readable storage medium, comprising:
The computer-
Instructions for causing a computer to receive a differential power control message based on an imbalance in power transmitted from multiple antennas of a user equipment (UE); And
Based on the message, instructions for causing the computer to compensate for the imbalance by varying the transmit power from one or more of the plurality of antennas, the computer-program comprising a computer-readable storage medium. stuff. 46. The method of claim 45,
And the message comprises a common value and a differential value. 47. The method of claim 46,
And compensating for the imbalance is based on the differential value. 47. The method of claim 46,
Compensating for the imbalance comprises a computer-readable storage medium based on a combination of the differential value and a previously received differential value. 46. The method of claim 45,
Compensating for the imbalance comprises a computer-readable storage medium further based on a current transmit power of the UE. 46. The method of claim 45,
The computer-
Instructions for causing the computer to determine a path loss based on received downlink path loss measurements for each of the plurality of antennas; And
Based on the measurement for each of the plurality of antennas, further comprising instructions for causing the computer to compensate for the path loss by varying the transmit power from one or more of the plurality of antennas. A computer-program product comprising a readable storage medium.

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